Product Revenue by Geographic Location and Percentage of Total Product Revenue (Detail) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 22,606,465	$ 14,766,611	$ 19,624,769	$ 14,360,660	$ 18,444,287	$ 18,455,817	$ 16,140,852	$ 11,737,679	$ 71,358,505	$ 64,778,635	$ 55,556,594
Percentage of revenue									100.00%	100.00%	100.00%
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									57,904,290	48,366,140	38,313,594
Percentage of revenue									81.10%	74.70%	69.00%
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									6,267,830	10,988,664	12,976,985
Percentage of revenue									8.80%	16.90%	23.30%
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									$ 7,186,385	$ 5,423,831	$ 4,266,015
Percentage of revenue									10.10%	8.40%	7.70%